Fig. 1.

Comparison between CA-SA ST398 and HA-SA ST239 isolates in adhesion, aggregation and virulence characteristics. a Colony counts of adhesive and internalized bacteria above in A549 epithelial cells infected for 2 h. A ~ 0.4-fold increase could be seen for HA-SA ST239 isolates compared with that for CA-SA ST398 strains. b Biofilm formation. Biofilm formation abilities were calculated by the semiquantitative biofilm assay and were read using a MicroELISA autoreader (BioRad) at 570 nm. An obvious increase could be seen for HA-SA ST239 isolates compared with that for CA-SA ST398 strains. c Hemolysis (erythrocyte lysis). Hemolytic activities were determined by incubating culture filtrates with human red blood cells. A significant increase could be seen for CA-SA ST398 isolates compared with that for HA-SA ST239 strains. *P < 0.05, **P < 0.01, ***P < 0.001 (unpaired t-test). The data is representative of three independent experiments